Negative chemical ionization mass spectra of polycyclic chlorinated insecticides

Dougherty, Ralph C.; Dalton, J. Christopher; Biros, Francis J.

doi:10.1002/oms.1210061103

Cited by 110 publications

(39 citation statements)

References 18 publications

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“…The principal positive reagent ions from methane, CH 5 + and C 2 H 5 + , react with almost all organic molecules, and methane CI spectra are largely independent of reagent gas pressure in the ion source [2,3]. When resonance electron capture (EC) ionization was adapted for negative chemical ionization (NCI) mass spectrometry, methane was used as reagent gas to thermalize electrons [4][5][6]. Although more efficient gases for EC-NCI-MS have long been identified [7], methane continues to be the most popular choice [8,9].…”

Section: Introductionmentioning

confidence: 99%

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

Newsome

Steinkamp

Giordano

2016

J. Am. Soc. Mass Spectrom.

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Abstract. As a reagent gas for positive-and negative-mode chemical ionization mass spectrometry (CI-MS), isobutane (i-C 4 H 10 ) produces superior analyte signal abundance to methane. Isobutane has never been widely adopted for CI-MS because it fouls the ion source more rapidly and produces positive CI spectra that are more strongly dependent on reagent gas pressure compared with methane. Isobutane was diluted to various concentrations in argon for use as a reagent gas with an unmodified commercial gas chromatograph-mass spectrometer. Analyte spectra were directly compared using methane, isobutane, and isobutane/argon mixtures. A mixture of 10% i-C 4 H 10 in argon produced twice the positive-mode analyte signal of methane, equal to pure isobutane, and reduced spectral dependence on reagent gas pressure. Electron capture negative chemical ionization using 1% i-C 4 H 10 in argon tripled analyte signal compared with methane and was reproducible, unlike pure isobutane. The operative lifetime of the ion source using isobutane/ argon mixtures was extended exponentially compared with pure isobutane, producing stable and reproducible CI signal throughout. By diluting the reagent gas in an inert buffer gas, isobutane CI-MS experiments were made as practical to use as methane CI-MS experiments but with superior analytical performance.

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Section: Introductionmentioning

confidence: 99%

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

Newsome

Steinkamp

Giordano

2016

J. Am. Soc. Mass Spectrom.

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“…The types of fragmentation observed have been reported (196)(197)(198). When methane is the reagent gas, fragmentation processes include the nucleophilic displacement of chlorine atoms by a negative oxygen atom (0-) (198).…”

Section: Electron Capture -Gas Chromatograph Calibrationmentioning

confidence: 99%

“…When methane is the reagent gas, fragmentation processes include the nucleophilic displacement of chlorine atoms by a negative oxygen atom (0-) (198). The oxygen atom arises from the presence of water, a contaminant of the methane.…”

Section: Electron Capture -Gas Chromatograph Calibrationmentioning

confidence: 99%

Investigation of the contribution of aquatic humus to the transport of DDT in the environment

Blunk

2000

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1982 ABSTRACTThe fate and transport of insoluble, hydrophobic organic pollutants in the aquatic environment constitutes a prominent area of concern. It is thought that pollutants of this nature may exist in association with organic carbon, which is predominantly aquatic humus. This type of association could significantly affect the kinetics of such transformation processes as volatilization or chemical and biological degradation of the pollutant. While dissolved organic matter (DOM) comprises the bulk of organic carbon (or aquatic humus) in natural waters, the interact·io',\ between naturally occurring DOM and insoluble organic pollutants has not been quantified.The work presented in thi s di ssertation is an effort to quantify the, effect of dissolved organic matter on the solubility in water and, hence, the transport of hydrophobic organic compounds (specifically, DDT) in the environment.Saturated aqueous solutions of DDT were generated by a method that is different from those used by other workers. Within a closed system, an excess of sol id DDT was allowed to vaporize and enter an aqueous solution through the gas phase. The concentraction of DDT in solution increased with time, 1 eve 1 i ng off when equil i bri urn and a saturated solution was established.The solubility of p,p'-DDT in distilled water was determined to be 1.87 ± .01 ppb. The solubility of the o,p'-DDT isomer in distilled water was determined to be 4.88 ± .03 ppb. The concentrations of p,pl-3 DDT and o,pl-DDT in distilled water solutions containing dissolved organic matter were definitely higher than the aqueous solubilities of these compounds. A minimum value for the DDT/DOM partition coefficient (Kp) in water was determined. This partition coefficient, when normalized to organic carbon, is referred to as Koc (K oc = Kp/fraction organic carbon). A minimum log Koc for both p,pl-DDT and o,pl-DDT was determined to be 4.7 ± .2 log units. Under environmental conditions, this partition coefficient indicates that the majority of DDT present in aqueous systems will be associated with dissolved organic matter.

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“…Depending upon the analytical objective, we employ one of two different reagent gas mixtures, namely: isobutane with traces of oxygen (3) or methylene chloride with traces of oxygen (4). The dominant ionization processes that occur in both of these gases are listed in Eqs.…”

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confidence: 99%

Negative chemical ionization studied of human and food chain contamination with xenobiotic chemicals.

Dougherty¹,

Whitaker²,

Smith³

et al. 1980

Environ Health Perspect

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Negative chemical ionization mass spectrometry with a mixture of isobutane, methylene chloride, and oxygen as the reagent gas has been used to explore contamination of environmental substrates with xenobiotic chemicals. The substrates in question, fish tissue, human seminal plasma, and human adipose tissue, were cleaned up by one of the following three cleanup procedures: (1) continuous liquid-liquid extraction steam distillation; (2) gel-permeation chromatography; and (3) adsorption on activated carbon followed by elution with toluene. The third procedure was used only for the examination of planar polychlorinated aromatic hydrocarbons in environmental samples. Using these techniques, we have found evidence for contamination of fish samples with polychloronaphthalenes, polychlorostyrenes, polychlorobiphenyls, polychlorodibenzofurans, and polychlorodibenzodioxins among other chemicals. The polychlorodibenzodioxins appeared only in the spectra of extracts of fish obtained from the Tittabawassee River at Midland Michigan. The polychlorodibenzofuran ions appeared in NCI mass spectra of fish that were significantly contaminated (above 2 ppm) with polychlorobiphenyls. Toxic substances occurring in human seminal plasma included pentachlorophenol, hexachlorobenzene, DDT metabolites, and polychlorobiphenyls. We have investigated toxic substances in human seminal plasma because of the apparent decrease in sperm density in U.S. males over the last 30 years.Results of screening human adipose tissue for contamination with xenobiotic chemicals have been largely coincident with results of the EPA human monitoring program. Polychlorobiphenyls, DDT metabolites, nonachlor, and chlordane have appeared in most samples examined. Detection limits for all of these chemicals were of the order of 1 ppb.

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Negative chemical ionization mass spectra of polycyclic chlorinated insecticides

Cited by 110 publications

References 18 publications

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

Investigation of the contribution of aquatic humus to the transport of DDT in the environment

Negative chemical ionization studied of human and food chain contamination with xenobiotic chemicals.

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